A lithium ion battery is a battery such that an Li ion moves between a cathode and an anode. The lithium ion battery has the advantage that energy density is high. In contrast, a sodium ion battery is a battery such that an Na ion moves between a cathode and an anode. Na exists so abundantly as compared with Li that the sodium ion battery has the advantage that lower costs are easily intended as compared with the lithium ion battery. Generally, these batteries have a cathode active material layer containing a cathode active material, an anode active material layer containing an anode active material, and an electrolyte layer formed between the cathode active material layer and the anode active material layer.
It is known that a carbon material is used as an anode active material used for these batteries. For example, in Patent Literature 1, a nonaqueous electrolyte secondary battery is disclosed, in which lithium iron phosphate represented by LixFePO4 is used as a cathode active material and a carbon material such that average action potential is 0.3 V or less on the basis of lithium is used as an anode active material.
Incidentally, in Non Patent Literature 1, K4Nb6O17 is disclosed as a photocatalyst material. Also, in Patent Literature 2, an electrode for a lithium secondary battery containing Li4Nb6O17 as an active material for an electrode is disclosed.